Answer:
C. an explanation of why an opposing argument is false
Explanation:
Rebuttal is the act of refuting something by making a contrary argument, or presenting contrary evidence.
If you make a rebuttal of a charge or accusation that has been made against you, you make a statement which gives reasons why the accusation is untrue.
Therefore, the best definition of rebuttal is the third choice (an explanation of why an opposing argument is false).
